This project attempts to achieve the following objectives: 1) Analyze joint, tendon and capsuloligamentous forces in normal and abnormal fingers and thumbs. 2) Study the pathomechanics of the fingers and thumb and their surgical treatment methods. 3) Perform objective functional evaluation of hand patients before and after treatment. 4) Correlate the predicted muscle forces and their EMG measurements. Normative models for each finger and the thumb have been established based on a precision biplanar x-ray method using marked cadaver specimens. The optimization technique combined with the permutation method and functional grouping have been adopted for force prediction. Quantitative EMG data on normal subjects has been used to correlate the theoretically estimated results. The cross-sectional technique was found to be ineffective in quantitating capsuloligamentous geometry, and it has been replaced by a stereo-video method using high resolution T-V cameras. Collateral ligaments of the MCP joints have been studied with improved results. Modeling of the joint capsuloligamentous structure will be achieved using equipollent force analysis. Cadaver finger and joint specimens will be tested on an MTS machine to determine joint contact points and ligament tension to facilitate mathematical modeling. Three groups of paitents are being evaluated using the objective method developed from this project to assess their functional deficits and treatment results. Normal subjects have also been studied to establish the reference data base. Hand pathological conditions involving joint deformation and strength loss are being studied. The results will be used to evaluate diagnosis and treatment of alternatives.